(1) Field of the Invention
The present invention relates to an optical disk device and optical disk recording method. More particularly, the invention relates to a technique of recording by driving a laser light source with a driving current suitably superimposed with a high-frequency current.
(2) Description of the Related Art
The optical disk device records and reproduces data by applying laser light on an optical disk. If, in this process, a part of the light reflected from the optical disk enters a laser diode as a light source, the incident light causes instable laser oscillation so that recording and reproduction characteristics of the device are deteriorated. Known as a countermeasure against this problem is a technique of effecting multimode laser emission by driving the laser diode with the driving current superimposed with the high-frequency current, thereby suppressing noises caused by a feedback light.
It is preferred that the amplitude of the high-frequency current superimposed on the laser driving current is set to a proper level according to each recording power or reproduction power applied at recording time or reproduction time. At the recording time, however, an output limit of the laser diode need be taken into consideration when setting the amplitude of the high-frequency current to the proper level.
As a technique related to this control, JP-A No. 2000-163782 discloses an arrangement wherein the amplitude or duty of the high-frequency component is changed between the recording time and the reproduction time and wherein at the recording time, an operation of superimposing the high-frequency component is controllably enabled or disabled according to a type of information to be recorded on a recording medium. Further, PCT Pub.No.WO2005/043521 discloses an arrangement wherein a high-frequency recording signal has a different level from that of a high-frequency reproduction signal and wherein the level of the high-frequency signal is changed a predetermined time prior to transition from a reproduction mode to a recording mode.